A known pump of the vane type is shown in the U.S. Pat. No. 4,373,871 of Feb. 15, 1983, wherein a pressure plate faces the inlet side of the drive shaft exposed to inlet pressure. Such pressure plate is contiguous to a pump package comprising a rotor, having valves encompassed by a cam ring. The pump package is contiguous with an additional pressure plate within the pump housing which closes the pump housing and is sealed therein by abutment with a sealing ring carried annularly within the housing. The pump package is thus sandwiched between a pressure plate on the inlet side of the pump and a pressure plate at the outlet side to minimize flow losses due to unavoidable production tolerances. In order to maintain a close relationship a spring is used to startup of the pump when there is insufficient outlet pressure. The pressure plate at the outlet side of the pump package is provided with a radial sealing ring, which is held in a relatively complex sealing support assembly around a drive shaft bearing. The sealing assembly effects compensation for larger axial sealing tolerances.